When E! News informed Demi of the surprise engagement, the Heart Attack singer joked: "I've told Kanye before that if he doesn't treat her well, I'm going to come after him."

The 21-year-old star continued: "With Kim, I've known her for years and she's been such a good friend to me in really really rough times.

"I'm happy to finally see her really happy and treated right. She deserves that Giants stadium!"

The blue-haired starlet added that as soon as the interview wrapped she was going to text Kim and offer her congratulations.

Kim and Demi have spoken previously of their friendship, which blossomed following Lovato's stint in rehab back in 2010.

Last year, Demi told Seventeen magazine: "Kim was there for me when not many people were," while the Keeping Up With The Kardashians star has called the young singer "a true friend" and "an inspiration".